A method to determine relative production rates of productive layers of a reservoir using quasi-steady flux temperature values measured along a wellbore is described in, e.g.: Ĉeremenskij G. A. Prikladnaja geotermija, Nedra, 1977 p. 181. Disadvantages of the method include low accuracy in determining the layers' relative flow rate, resulting from the assumption that the Joule-Thomson effect does not depend on time and is the same for different layers. In fact, it depends on the formation pressure and specific layers pressure values.